Lightness of Water Vapor Influence Air Temperature and Cloud Cover, Making Global Climate Models More Accurate

Global climate models are the principal instruments for studying the Earth's climate, forecasting future changes, and informing climate policy.

However, climate models frequently disagree on the specific degree of future warming, owing to differences in how clouds are represented.

According to main author Da Yang, an associate professor of atmospheric science at UC Davis and a faculty scientist at Lawrence Berkeley National Lab, climate models are the finest tool we have for predicting future climate change.

It is critical that we actively work to enhance them.

Does cold air rise?

(Photo : Billy Huynh/Unsplash)

While popular thinking holds that hot air rises, the study finds that the opposite is true in the tropical environment, as per ScienceDaily.

Yang and his colleagues previously hypothesized that cold air rises in the tropics because damp air is lighter than dry air.

This is known as vapor buoyancy, and it controls the number of low clouds that form over the subtropical ocean.

"Vapor buoyancy determines the distribution of low clouds - the sort we find off the California coast, which contributes significantly to the global energy balance," Yang explained.

Clouds are the most difficult problem in effectively projecting future climate change, therefore we must get vapor buoyancy right.

According to the study, six of the 23 frequently used climate models assessed do not currently include this impact since water vapor is a trace gas with a minimal buoyancy effect.

However, the study demonstrated that the vapor buoyancy impact is more considerable than previously thought.

Low cloud cover in climate models without vapor buoyancy can be incorrect by up to 50% in some places.

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How can clouds influence climate change?

Because they reflect so much sunlight, low clouds are among the most significant clouds for climate change and the planet's energy balance.

Fewer low clouds can result in more sunshine being absorbed and a warmer planet. More low clouds may result in a colder scene.

Yang predicted that when temperatures rise, the buoyancy effect of water vapor will become more relevant due to increased atmospheric water vapor.

More research is needed to understand how water vapor buoyancy governs Earth's climate.

Seth Seidel, a UC Davis graduate student, and Wenyu Zhou, a former member of Yang's group who currently works at the Pacific Northwest National Laboratory, are also co-authors on the paper.

Clouds have two significant effects on climate. For starters, they are a crucial component in the water cycle.

Clouds act as a conduit between rain and snow, seas and lakes, and plants and animals.

Second, clouds have a significant impact on Earth's temperature.

But it gets more complicated: clouds may both cool and raise the Earth's temperature, as per NASA Climate kids.

Clouds may obstruct the Sun's light and heat, lowering the Earth's temperature. On a cloudy day, you've undoubtedly seen this type of cooling.

However, some of the Sun's heat does reach Earth. The heat from the Sun can be trapped by clouds.

Even when there is no sunlight, clouds continue to retain heat. It's as though clouds are covering Earth in a large, warm blanket.

As a result, clouds can have both a cooling and a warming influence.

When it comes to the Earth's temperature, do clouds warm more than they chill, or vice versa? That is dependent on where the clouds are in the Earth's atmosphere.

Within a mile or so of the Earth's surface, clouds tend to cool rather than warm. These lower, heavier clouds mostly reflect the heat of the Sun. This cools the planet's surface.

Clouds high in the atmosphere have the opposite effect: they warm rather than cool the Earth. Some of the Sun's heat is trapped by high, thin clouds. This heats the Earth's surface.

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